pkg/test: cleanup imports

lib/src/runner/runner_suite.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 
 import 'package:async/async.dart';
 
+import '../backend/group.dart';
 import '../backend/operating_system.dart';
 import '../backend/suite.dart';
-import '../backend/group.dart';
 import '../backend/test.dart';
 import '../backend/test_platform.dart';
 import '../utils.dart';
 import 'environment.dart';
 
 /// A suite produced and consumed by the test runner that has runner-specific
 /// logic and lifecycle management.
 ///
 /// This is separated from [Suite] because the backend library (which will
 /// eventually become its own package) is primarily for test code itself to use,
@@ skipping 76 matching lines @@
     _onDebuggingController.add(debugging);
   }
 
   /// The backing function for [suite.close].
   Future _close() => _closeMemo.runOnce(() async {
     _onDebuggingController.close();
     if (_onClose != null) await _onClose();
   });
   final _closeMemo = new AsyncMemoizer();
 }